This blog provides updated forecasts and comments on current weather or other topics

Tuesday, December 14, 2010

Last Night's Squall Line

Last night, between roughly 12:00 and 1:00 AM (depending on where you were) an intense line of thunderstorms and strong winds moved across the Washington coast and swept across western Washington. Winds gusted to 60-70 mph along the coast and to 40-50 mph in places across the interior. A significant number of trees were toppled plus innumerable loss of branches, resulting in power outages affecting thousands of people. Thousands are still without power Tuesday evening. And there was quite a bit of lightning too.

The cause a line of thunderstorms associated with a strong cold front. Here is the radar image at around 12:30 AM (and a close in shot as well). The strongest rain associated with the line is indicated by red color (very, very heavy rain is associated with reds!)

There was a considerable change in virtually all weather parameters with this front. Here are the observations at the top of the atmospheric sciences building here at the UW (click to expand). The winds gusted to 40 mph (top line), the wind direction shifted abruptly to the south, temperature plunged by 6F, pressure spiked upwards (fifth line), and lots of precipitation fell. My dog was terrified.

Was this predicted? Not really. We knew a strong front with good rain was coming in, but did not foresee such an intense event. But with a coastal radar we probably would have seen it coming and been able to provide a few hours warning.

The number of tree losses was undoubtedly aided by the saturated soil. Wet soil has less adhesion to roots...less holding power...making it easier to wind to do its dirty work.

The weather should calm down a bit now, with the jet stream and most of the action going into California, for the next few days.

AND...today there was an F2 tornado at Aumsville, 10 miles NE of Salem, Oregon.

My station on the eastern waterfront, Bainbridge Island measured an instantaneous rain rate of just over 9 in/hr for 3 minutes straight from 12:29am-12:32am. This was the highest rain rate I have recorded in 8+ years of continuous monitoring in the area!r

Winds in Eatonville gusted to 65 mph. The raindrops were so big I thought they were hail. But when I went out on the deck to check it was just rain! I didn't see any lightening....and if there was thunder I don't think I would have heard it over the wind! That was an amazing storm! Too short though! And why do the good storms always seem to happen at night?!!!!

It gusted a little in Bellingham near midnight but the real action was at 7:00 am today. Oddly, the NWS only registered gusts of 24mph but it sounded furious, there was 1/4 inch of hail pelting the windows horizontally and a nearby lightning strike. Is it possible there was a microburst that wouldn't register at the airport?

Cliff, We (wife and I) always look forward to your posts. We noticed very green lightning last night moments before the stuff hit the fan. Have seen lots of lightning, never brilliant green before.

On the coastal radar issue, I really glad this is happening. While others may believe ignorance is bliss, intelligence shall prevail. Have been serious weather geeks for over a decade after taking a course from Michael Carr and Lee Chesneau. Thanks!

The sound last night was what really surprised me. At our house there was wind, rain, and a sound like the horn of a semi truck that lasted for several minutes. I heard it move away with the rain. Quite freaky...

Anyone else hear the freight train sound at midnight? Maybe that is what @Frith heard. Friends in West Seattle (who grew up in tornado country like I did) also heard the rain + hail+ freight train sound and were ready to head to the basement. We're in Ballard.

Best thunder and lightning I've seen in a couple years here. I was very happy to still be awake and watching the show through our south-facing big living room window in Kirkland (which looked like a car wash with all the water blowing against it!).

The wind reminded me of some of the gusts from the December 2007 event, particularly in the way that it swept by. I could see green transformer flashes to the south and watched as they progressed ever closer until one in the neighborhood blew, then as the wind passed to the northwest, the endless green flashes continued on with it like a wave. I distinctly remember a similar progression in 2007.

We have a running joke going on Sinclair Island where whatever the Weather Service is forecasting for wind speed for the next day, just double it and that gives the accurate figure. This works for all wind directions. Yesterday they were forecasting winds of 5 - 15 mph for the islands so it did not surprise me that it blew steady at 20 most of the day with gusts to 30. I don't believe this is related to lack of radar on the coast. It is more a chronic underestimating of the winds in this area.